Multiple lock systems are used to allow access to an area by multiple users while preventing access to unauthorized persons. Such systems may be used, for example, on property with oil and gas leases, hunting leases, or wireless communications towers. One advantage of multiple lock systems over a single lock system is that a user authorized to access multiple areas may use locks with the same key for each area, eliminating the need for that user to carry multiple keys and reducing confusion over which key provides access to which area. Another advantage is that when a user is no longer authorized to access the area, the user's lock can be replaced or eliminated, and the distribution of new keys to all of the other users is not required.
One simple prior known multiple lock system uses a chain around a gatepost and a post on a gate secured by multiple padlocks linked in series with each user having their own padlock and key. One disadvantage of this system is that a user may bypass one or more locks when resecuring the chain, thereby preventing access to the users of the bypassed locks. Another disadvantage is that one user can remove the whole system. Detection of an unauthorized lock, added by cutting the chain and inserting the lock, is very difficult with this system.
U.S. Pat. No. 2,707,125 to Ritter discloses a tubular multiple padlock system that mounts on a gatepost. U.S. Pat. No. 3,889,497 to Tuttle discloses a plate type multiple padlock device where padlocks must be used in multiples of four. U.S. Pat. No. 3,988,031 to Meyer and U.S. Pat. No. 4,997,219 to Carter disclose vertical wheel type multiple padlock devices where removal of a peripheral padlock provides access to a hole that allows retraction of a locking bar. U.S. Pat. No. 4,697,443 to Hillin discloses a horizontal wheel type multiple padlock device having radial access channels with a fastening gate for each padlock. U.S. Pat. No. 5,868,015 to Eaker discloses a multiple padlock system with a locking bar and a plurality of coupling segments. Each of the above patented devices is relatively complex and expensive.
Accordingly, there is a need for a simple multiple padlock system that cannot be readily removed by a single user. The multiple lock system should also prevent bypassing any user's padlock and addition of unauthorized padlocks. The system should be resistant to boltcutters and sledgehammers.